In a conventional two-way or two-direction control valve, the control piston is spaced axially at some distance from the valve member mounted in a special control housing. The control piston has one piston rod on each side. The piston rod adjacent to the valve member has a valve surface which cooperates with a valve seat in the valve member. The control valve of this assembly controls fluid flow through a communication bore between the side of the valve member adjacent to the control piston and the cover surface adjacent to the valve seat of the valve member and offset relative to the other cover surface of the valve member. The lengthwise bore in the valve member is provided with a constriction.
In conventional valves, the opening and closing speeds are different from each other, and are dependent upon the diameter of the constriction and the pressures on the surface adjacent to the valve seat and the engaging annular surface. The known valve opens for flow only in one direction. When the valve member is lifted from its seat, the pressure medium flows past the valve and flows to its offset cover surface. Since the control piston is separated from the valve member, the position of the valve member does not always correspond to the position of the control piston.